Norepinephrine is recognized as a neuro-transmitter implicated in the vascular resistance increases of spleen and kidney following reflex stimulation by acute hypovolemia. In previous studies carried out with support from this grant, we have shown that vascular resistance in spleen and kidney is increased by acute hypovolemia. Further observations have established that this increase can be prevented by right adrenalectomy coupled with left adrenal denervation; a set of circumstances which decreases circulating norepinephrine levels and decreases splenic and renal norepinephrine uptake. Currently we are evaluating vascular resistance patterns in response to hemorrhage of dogs with acutely denervated spleen and kidney. These data are still incomplete, difficult to achieve in a physiologic setting but suggest that when neuronal norepinephrine uptake is prevented by acute denervation, vascular resistance will not always rise in response to hemorrhage. In the denervated organs whose vascular resistance is raised by hemorrhage, extra-neuronal mechanisms are operating. There is no net norepinephrine uptake in these acutely denervated organs. In the next grant year, we plan to investigate the effect of adrenal medullary deprivation (right adrenalectomy and denervated left adrenal) on vascular resistance changes of spleen and kidney mediated from isolated innervated carotid sinus preparations. BIBLIOGRAPHIC REFERENCE: Reflex stimulation of peripheral norepinephrine release; effect of nephrectomy and a physiological rate of angiotensin II infusion. Prager, R.L., Seaton, J.F., and Harrison, T.S. Surgical Forum 18:187-190, 1975.